Rotary machinery such as high speed turbo machinery typically include rotors which are subject to radial excursion such as by vibration or synchronous or non-synchronous exitation. In certain applications of such turbine machinery, such as may be utilized in an aircraft application, the rotor may have a duty cycle requiring it to function for a limited period of time in the event of internal damage during operation thereof which introduces a substantial weight unbalance on the rotating unit.
One well known effective manner of accommodating certain radial motion of the rotating unit is the utilization of fluid film damping apparatus associated with the bearing carrying the rotor. Incompressible fluid such as oil is introduced into an annular chamber surrounding the outside of the bearing. Radial motion of the bearing relative to the chamber creates hydrodynamic pressure therein to oppose radial movement. The shearing action occurring upon the liquid effectively dampens the radial motion. Characteristically, such a damping system which may be referred to as a separate damping system, is disposed and arranged such that it accomplishes this single, sole purpose, in contrast to dampers within the bearing itself which also must be designed to function as a portion of the bearing.
One drawback to existing radial bearing dampers is their limited ability to accommodate shaft excursion. More specifically, the hydrodynamic pressure build up and fluid shearing action effectively occurs only when the radial space becomes very, very narrow. Furthermore, known hydraulic fluid bearing dampers do not readily produce mechanical restoring forces within the damper which are necessary for their continued operation.